Overview

Comprehensive Description

Description

This creature looks more like a plant than an animal. It is a colonial bryozoan that may form either diffuse branching chains or develop into dense clumps. During the peak of the growth season (summer), colonies have the appearance and texture of velvet. Individuals within a colony vary in shape and size. Attached zooids posses a roughly oval base and a cylindrical peristome (erect tube). Erect zooids may be cylindrical of slightly bulbous at the base. In dense colonies the zooids may be as short as 0.3 mm and in diffuse colonies they may reach 1 mm long.

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Colonies of V. pavida develop as chains of zooids connected by the stolon that arises from the base of new zooids. In young colonies, overall morphology of the colony is quite simple; however, as they develop, zooids elongate and bud off new stolons and zooids to form extensive networks. Individual zooids are cylindrical and measure approximately 0.15 X 0.60 mm. In older colonies, zooids can measure as much as 2 - 3 mm (Winston 1982). The lophophore averages 0.37 mm in diameter and bears 8 tentacles.

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V. pavida is a cosmopolitan species whose range in the western Atlantic extends from Chesapeake Bay to Brazil. Prior to Winston's (1982) study, this species had not been documented in the India River Lagoon. During the study, it was collected only once, at Link Port, approximately 7 miles north of Ft. Pierce Inlet, but it is likely to be distributed in brackish areas throughout the India River Lagoon (Winston 1982).

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Look Alikes

Colonies of V. pavida resemble those of the genus Bowerbankia. These groups are differentiated based on differences in growth from the stolon. In Bowerbankia, new zooids are budded separately from the stolon; in Victorella pavida, the stolon arises from the base of zooids.

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Ecology

Habitat

Found in areas of low and fluctuating salinity such as estuaries and lagoons. The trembling sea mat grows in shallow water on submerged stones, plants and wood as well as artificial substrata such as concrete.

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Trophic Strategy

V. pavida, like all bryozoans, is a suspension feeder. Each individual zooid in a colony has 8 ciliated tentacles that are extended to filter phytoplankton less than 0.045 mm in size (about 1/1800 of an inch) from the water column. Bullivant (1967; 1968) showed that the average individual zooid in a colony could clear 8.8 ml of water per day.Habitats: In the IRL, V. pavida was collected only from seagrass beds around Link Port.

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Associations

Seagrasses as well as floating macroalgae, provide support for bryozoan colonies. In turn, bryozoans provide habitat for many species of juvenile fishes and their invertebrate prey such as polychaete worms, amphipods and copepods (Winston 1995).Bryozoans are also found in association with other species that act as supporting substrata: mangrove roots, oyster beds, mussels, etc.

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Relevance to Humans and Ecosystems

Benefits

Benefit in IRL: Bryozoans are ecologically important in the Indian River Lagoon due to their feeding method. As suspension feeders, they act as living filters in the marine environment. For example, Winston (1995) reported that bryozoan colonies located in 1 square meter of seagrass bed could potentially filter and recirculate an average of 48,000 gallons of seawater per day.